McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
3. Similar Triangles
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Exercise 38 Page 568

Notice that △ XYZ is similar to △ YWZ by the Angle-Angle Similarity Theorem.

YW=5sqrt(2)/2

Practice makes perfect

We are given the right triangle XYZ. We know that both legs of △ XYZ measures 5 and YW is an altitude of this triangle. Let's recall that an altitude is always perpendicular to the base of a polygon. Let's take a look at the diagram.

We can see that △ XYZ and △ YWZ have one common angle, ∠ Z. Moreover, both triangles have a right angle. Therefore, the triangles have two congruent corresponding angles. This means that △ XYZ and △ YWZ are similar by the Angle-Angle Similarity Theorem. △ XYZ ~ △ YWZ Recall that in the similar triangles corresponding sides are proportional. YW/XY=YZ/XZ To find the length of YW, we will first find the length of XZ. To do so, we will use the fact that △ XYZ is a right triangle and apply the Pythagorean Theorem.
XY^2+YZ^2=XZ^2
5^2+ 5^2=XZ^2
Simplify
5^2(1+1)=XZ^2
5^2(2)=XZ^2
sqrt(5^2(2))=sqrt(XZ^2)
sqrt(5^2)*sqrt(2)=sqrt(XZ^2)
5*sqrt(2)=XZ
5sqrt(2)=XZ
XZ= 5sqrt(2)
Now, we will substitute the lengths of the segments into the proportion to find the length of YW.
YW/XY=YZ/XZ
YW/5=5/5sqrt(2)
Simplify
YW=5/5sqrt(2)*5
YW=1/sqrt(2)*5
YW=5/sqrt(2)
YW=5/sqrt(2)*1
YW=5/sqrt(2)*sqrt(2)/sqrt(2)
YW=5sqrt(2)/(sqrt(2))^2
YW=5sqrt(2)/2
The length of YW is 5sqrt(2)2.